This invention relates generally to cargo loading systems, and particularly to means and methods for loading cars in railroad transportation systems at preselected loading stations.
Recently, railroad transportation systems have been devised for transporting small cars or dollies in freight handling and distribution areas such as, for example, between loading docks and distribution areas in manufacturing and processing plants. These railroad systems typically include a circuitous system of tracks which extend from aside one or more cargo loading docks past a series of stations at which the cargo may be unloaded. A conveyor belt typically extends from the loading dock to the periphery of the area exteriorly of the building in which the circuitous track is located at which periphery a warehouse or conventional loading dock is located for receiving cargo from trucks or interstate railroad cars.
The cars or dollies used in such railroad transportation systems are frequently controlled by programmed computers. Such automated systems minimize the need for manual car drive control as well as for manual handling of cargo at the loading dock and distribution stations. Equipment has thus heretofore been devised for automatically halting cars on the tracks aside the docks and distribution stations, for urging cargo on or off the cars, and then for driving the cars from the loading dock or stations leaving the stations ready to receive other cars.
Notwithstanding the highly desirable automation features provided by the just-described systems, in actual practice the systems have failed to perform their loading and unloading function effectively. In practice cargo is typically handled as individual modules supported upon individual pallets which must be urged completely onto and off the cars at the loading stations. Where such action is not fully accomplished a portion of the cargo carrying pallet is left overhanging the loading side of the car where it becomes susceptible of being snagged by structural components of the station itself as the car departs the station or approaches the next successive station. This action may well cause the cargo to fall from the car or loading dock and be damaged. Even where such overhanging cargo successfully leaves and approaches the loading stations, it may, nevertheless, encounter structural objects adjacent the tracks between stations and be knocked to the floor. In some cases the cargo may even fall from the car without encountering a stationary object such as when rounding a curve in the tracks.
Efforts have been made to alleviate the just-described problems by employing conveying means on the car itself. Such means are typically driven when the car is positioned at a loading station by a pair of friction wheels which abut one another at the loading station to transmit a driving force between the wheel located at the dock and the wheel located on the car. With this system, however, the friction wheel located at the loading station must impart substantial lateral force against the friction wheel on the car in order to prevent slippage between the two wheels. This lateral force is so strong as often to cause the car to tilt away from the loading dock which serves to endanger the security of cargo on the car, to create danger of car derailment, and to uncouple the conveyor means on the car from that on the dock.
Accordingly it is a general object of the present invention to provide improved means and methods for loading and unloading cars in railroad transportation systems.
More specifically, it is an object of the invention to provide a cargo loading system by which cargo may be conveyed at a loading station onto and off a car without leaving a portion of the cargo overhanging the car as a result of incomplete cargo transfer.
Another object of the invention is to provide means for loading a car having cargo conveyor means mounted thereon from a loading dock also having cargo conveying means located thereon which loading dock conveyor means drives the conveying means disposed on the car with positive driving action.